The present invention relates to a method for transferring additional services in a radio link network.
The present invention also relates to a radio link network for transferring additional services.
Radio links are nowadays a common method for transfer of telephony and data information. Radio links are often connected so that complete transmission networks with several integral links are created. The traffic originates for example from an exchange and the radio link network distributes the telephony traffic towards the subscribers in a successively more closely meshed network of links. Other common applications are mobile telephony where the radio link is used for distribution to remote or inaccessibly situated base stations (e.g. high terrain areas or urban areas where it is difficult and expensive to use existing ground communication). When an operator chooses to use a radio link for his commercial traffic transmission needs (e.g. data and telephony between the subscribers of the operator), he also has a need to transfer additional services, that is information connected with e.g. operational support for the equipment or service and data channels for communication between his own facilities.
The reason for not including these additional services in the regular commercial traffic is that a standard for how this type of information shall be included is often lacking and that the equipment that would be needed in every radio link terminal to separate the commercial traffic and the additional services is too expensive. The consequence of this is that all modern radio links include separate channels for transfer of additional information, normally 1-3 extra voice/data channels and channels for transfer of operational support information such as alarms and other supervising information.
In present day radio link systems there are terminals in each end of a radio link hop. On each radio link terminal there are connectors for connection of service channels (e.g. telephony), data channels and supervising equipment. In addition to these terminating points there are also connectors for commercial traffic and power supply. In the terminals there is also space for the terminating units which shall physically and electrically adapt the additional services to the transport system/radio link.
If the radio link hops are located close to each other forming chains or networks, the additional services must be connected by separate cabling between the radio link terminals in order to be able to distribute the information to the next radio link hop.
The presently used radio link systems have a number of drawbacks:
In all radio link terminals the additional services must be terminated in order to be transferred to the next radio link terminal via separate cabling even at places where the services are not used. This means an increased cost for the complete system.
The cabling becomes complex as all services need separate wires between the radio link terminals. Often the information will be distributed to several terminals which makes the installation work more complex and increases the risk for cabling mistakes.
In an installed radio link network it is difficult to incorporate new services as both the radio link terminals and the cabling there between have to be changed.
In spite of the drawbacks all known radio links use this method to transfer, terminate and distribute additional services.
For transfer of the additional services (and commercial traffic) over the radio link hop, time or frequency division is used so that the information from each additional service occupies one separate channel. If, as an example, a number of service channels for voice or data information are to be transferred, each channel is assigned its own fixed time slot in the flow of information between the radio link terminals. Alternatively they can be frequency modulated xe2x80x9conxe2x80x9d the commercial traffic. This system involves among other things the following drawbacks:
In order to avoid supplementary modifications to the radio link stations, each radio link station is equipped with one or several channels for additional services whether they are used in a certain application or not. This results in an unnecessarily expensive and complex product.
The fixed channel division of the transport system often results in the available channels having insufficient capacity or are of the wrong type.
Certain types of additional services, for example data and operational support information, are of a non-continuous type, i.e. the information arrives intermittently. However, the interruptions in the information can not be used because every service uses a separate, permanently assigned channel.
The object of the present invention is therefore to provide a transfer of various numbers and types of additional services in a radio link network without the need to increase the normal equipment of the radio link terminals. With this invention, the cabling between the terminals can also be simplified and it is not necessary to change it even if the number of additional services is increased. In addition, the invention implies that the available time and/or frequency range in the radio link system is used in a more efficient way.
Said object is achieved by a method according to the present invention, by which, in a radio link network in which information is transferred in a plurality of channels and which comprises a plurality of radio link stations, other traffic in the form of information from a number of additional services is transferred. Information from additional services is transferred in a common channel which can transfer information from various types of additional services, and the information from the additional services is transferred in the common channel between a starting point and an ending point without being terminated in a radio link station intermediate between the starting and ending points.
Said object is also achieved by a radio link system according to the present invention, comprising a plurality of radio link stations in which, in addition to regular commercial traffic, other traffic in the form of information from a number of additional services is transferred. The radio link stations include a terminating unit, at a starting point for a respective additional service, for physically and electrically adapting the information from the additional service to the radio link network and for splitting that information into packets; a controller for bringing packets from various additional services together in a common channel arranged in each radio link station, the common channel being for transferring information from various types of additional services; and a terminating unit, at an ending point for a respective additional service, for converting the information to a predetermined physical and electrical format.